It is the task of the invention to create a possibility, which on the one hand allows for a rapid as possible start-up of the internal combustion engine and on the other hand requires the least possible electrical output. It is additionally the task of the invention to further reduce the starting noise.
The task is thereby solved by a procedure of the kind mentioned at the beginning of the application; in that during the start-up, the direct starting control device for the generation of a combustion torque and the electrical starter for the generation of a starter torque are at least periodically activated simultaneously. In this way the power output of the starter is controlled as a function of the current combustion torque.
This then results in the starter being continually operated only at the currently required power output. For this reason the electric starter is controlled in an open- or closed-loop in such a way that the current total torque resulting from the current combustion torque and the current starter torque does not undershoot a specified set point torque. Thus, it is possible to generate by means of the electric starter just as much torque as is necessary for a reliable start-up of the internal combustion engine. This allows for a deployment of the starter, which is especially free from wear. By operating the starter continually only at the power output required at the moment, the noise level of the starting process can furthermore be effectively reduced. In addition the vehicle electrical system is thereby stressed only to the point which is necessary for a reliable start-up of the internal combustion engine.
When the procedure according to the invention is used, the torques do not, however, need to be explicitly acquired. On the contrary, the open- and/or closed loop control of the electrical starter is preferably implemented as a function of an acquired time, a current engine temperature, a current vehicle electrical system voltage, a current crankshaft or camshaft position of the internal combustion engine, a current rotational speed of the internal combustion engine, a current increase in engine rotational speed, a specifiable set point torque, a current total torque and/or a current compression torque. This makes it possible at least indirectly to make an inference about the torques previously mentioned. Parameters of this kind particularly allow for an even improved execution of the procedure according to the invention. It can, for example, be determined by means of a current time if the starter is initially suppose to generate an especially large starter torque in order to achieve as quickly as possible a relatively large combustion torque, from which the starter torque could then be significantly reduced. It can also be determined by means of the same current time if the starter is initially suppose to generate only a very small starter torque in order, for example, to be able to move the internal combustion engine just exactly into a crankshaft or camshaft position, from which the generation of a combustion torque is possible. Provision could also be made at this point to provide for varying set point torques as a function of a current time. A current engine rotational speed can be alternatively or additionally acquired to a current time.
It is particularly advantageous if a current crankshaft or camshaft position of the internal combustion engine, which is indicated, for example, in the form of crankshaft angle, is used for the open-loop control of the starter and in so doing for the starter torque. For example, the starter can in this case then always produce a specified starter torque if the internal combustion engine is located in a crankshaft position, at which one cylinder is the compression phase and had not yet advanced beyond the so-called top dead center.
By means of an engine rotational speed increase, inference can, for example, be made about a current total torque. During a particularly rapid increase in engine rotational speed, the starter torque can then be accordingly reduced or entirely deactivated.
If a current vehicle electrical system voltage is acquired and it turns out that it is relatively low, provision can thus be made to have the starter produce a part of the total torque, which is as small as possible, so that the starting process is in fact possibly lengthened but nevertheless provides for a reliable start-up of the internal combustion engine.
According to an advantageous form of embodiment of the procedure according to the invention, the direct injection device is activated, and the electric starter is subsequently activated as a function of a specifiable event. The event can in this case preferably be described by the elapsing of a specifiable period of time, the achievement or non-achievement of a specifiable engine rotational speed, the achievement or non-achievement of a specifiable increase in engine rotational speed, the achievement of a specifiable crankshaft or camshaft position of the internal combustion engine or the achievement or non-achievement of a specifiable total torque.
This makes it possible to once again reduce the deployment of the starter because a compression torque is initially produced, by means of which the internal combustion engine can be already set into rotational motion. In order, however, to still keep the start-up as short as possible, the electric starter can be activated after a certain number of revolutions of the internal combustion engine or after a specifiable time period has elapsed in order to achieve by means of the starter torque, which is thereby generated, a then specifiable set point torque.
Preferably the electric starter is at least activated in the instance if the compression torque is not sufficient to allow for a reliable piston sweep of top dead center in a subsequent cylinder with regard to a present combustion cycle. In so doing, on the one hand the starter is activated only for a short time and has a power consumption, which is as small as possible, in that it is controlled in an open-loop in such a way that it only supplies a proportion as small as possible to the total torque. On the other hand, a reliable start-up of the internal combustion engine is, however, still continually possible.
According to another advantageous form of embodiment of the procedure according to the invention, the electric starter is initially activated; and the direct starting control device for the implementation of at least one combustion cycle in at least one cylinder is subsequently activated as a function of a specifiable event. In this case, the internal combustion engine can initially be set into rotational motion by means of the electric starter. The direct starting control device can in this case then be activated, if this would allow for an especially efficient combustion. This is often only possible upwards from a certain engine rotational speed.
The direct starting control device is activated in this case for the implementation of at least one combustion cycle in at least one cylinder, so that a reliable piston sweep of top dead center in a subsequent cylinder with regard to the present combustion cycle is made possible. Consequently the starting torque is precisely so selected that a revolution of the internal combustion engine up to a crankshaft or camshaft position is possible, at which a combustion cycle can take place.
The internal combustion engine requires an especially large torque in each compression phase of each cylinder before sweeping top dead center in order to be set in rotational motion. This increased torque is preferably thereby achieved, in that a combustion cycle is introduced by way of the direct starting control device exactly when this increased torque is necessary. When this happens, the starter torque can often be immediately reduced. Because often only a very small combustion torque or no combustion torque at all is present especially when the number of revolutions is very small between two consecutive combustion cycles, the starter can be actuated in these crankshaft or camshaft positions of the internal combustion engine in such a way that a larger starter torque is again generated.
The starter torque is advantageously controlled in an open-loop in such a way during the starting process that an optimal total torque can be achieved. Preferably at least one optimizing criterion is used for the determination of the optimal total torque. The set point torque, for example, can be specified in such a way that a starting time period, which is as short as possible, can be achieved. The starting process can furthermore be optimized to such an extent that a heat loss, which, for example occurs on the cylinder wall during a combustion cycle, is kept as small as possible. The latter is basically possible then if the combustion cycles take place consecutively as rapidly as possible. For this to occur, a greater rotational speed of the internal combustion engine is therefore necessary.
Additional optimizing criteria comprise the possible wear on the starter, the maximum peak power consumption of the electric starter, the total power consumption of the electric starter during the starting process, the start-up noise as well as the starter noise. These criteria can be especially well used in developing an open- and/or closed-loop strategy for the electric starter and in so doing for the starter torque, which is to be generated.
The necessary specifiable parameters for the open- and or closed-loop control of the starter are advantageously stored by means of at least one engine characteristic map, one truth table or one neural network. These parameters comprise, for example, the optimizing criteria, the possible events as well as the specifiable set point torques.
The task is thereby additionally solved by a control unit as well as by an internal combustion engine of the kind mentioned at the beginning of the application, in that the control unit or the internal combustion engine is designed to implement the procedure according to the invention.
The task is also solved above all by a computer program of the kind mentioned at the beginning of the application, in that the computer program is programmed for the implementation of the procedure according to the invention if the computer program is run on a computer. In so doing, the computer program depicts the invention just as well as the procedure, for whose execution the computer program is programmed.